We have been studying inflammation ad immunity in the Syrian hamster and from the aspect of humoral and cellulr immunity. The hamster spleen is deficient in both humoral and cellular responses when compared to peripheral lymph node. A cell population (nylon wool adherent) normally present in spleen was capable of suppressing antigen specific proliferation. IgG1 and IgG2 antibody synthesis also appears suppressed in the intact spleen. However, the presence of sensitized precursor cells in spleen were detectable by in vitro culture or transfer to x-irradiated recipients.